Synchronous rectifiers have provided an elegant solution to applications that demand improved power density and efficiency from the power converter. Semiconductor switches such as Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), Insulated Gate Bipolar Transistors (IGBTs) can be produced with tiny conduction resistance such that when they replace rectifier diodes significant efficiency improvements and reductions in heat dissipation can be realized.
However, the synchronous rectifiers also bring one problem—a large voltage spike and high frequency ringing across a synchronous rectifier's drain and source. The voltage spikes can be caused by the poor reverse recovery characteristics of the body diodes of the synchronous rectifiers. In some applications, severe voltage stress can be imposed on the synchronous rectifiers due to the voltage spikes. One approach can include using rectifiers with voltage ratings that are high enough to withstand a worst case scenario voltage spike to prevent the breakdown of the synchronous rectifiers. However, this type of approach to the high voltage spike issue generally includes using rectifiers having much higher conduction resistance than a nominally rated rectifier, resulting in an increase in conduction losses.